If you have the mechanical linkage, you may have the same problem I had on
my first BB, which was a 1981. If you pull the door shut a bit too vigorously,
the linkage will go over center and lock - just like you lock it when you start driving.
On mine, there was a little hinged flap -- a plain hardware store hinge, really --
that could be folded down to keep the lever from moving to the over-center position.
I learned to secure that hinge in the down position with tape to keep friends from
locking us out. If this is your problem, you may need to rig up such a "stop",
and use it religiously. Better yet, put a spring on it, so it always goes to NO-LOCKOUT
when you open the door after driving.

Ok ya sorry I meant 98 but there basically still the same as 89, anyways yeah it to bad there isn't some kind of button release on the outside like the new buses that would be so much easier and i do have that flap

There have been a couple of posts on here about people rigging up cable and pulley systems to open their doors. You might want to run a search on that. I know Jason (lapeer20m) had also used a remotely operated air cylinder for his door. A cheap universal keyless entry kit will allow you to trigger a linear motor, air solenoid, or whatever to open the door. Just remember that this all comes at the expense of security. It might be a pain, but atleast I know that when I close my front door, the bus is locked up tight (I have a big lock on the back as well). If I recall correctly, Jason had to rig up a small air compressor to keep his system pressurized an dsecure over extended periods of time.